The other alternatives are attractive in theory but in practice are either impractical or offer only marginal improvements.

其他替代方案在理论上很有吸引力，但在实践中要么不切实际，要么只能提供微不足道的改进。

youdao

The most striking claim associated with the theory - that cuts in marginal rates could generate so much extra work effort that tax revenue would rise - is unlikely to apply except in extreme cases.

该理论被抨击最多的见解是削减边缘税率可以造成许多额外的工作效果，这会导致税收增加，但除却在极端情况下之外，这种说法很难适用于一般情况。

youdao

I mean, really, when was the last time you found someone who wanted to discuss the theory of relativity or the law of diminishing marginal returns?

我的意思是，说真的，上一次有人愿意与你讨论相对论或边际效益递减规律是什么时候呢？

youdao

And what that survey seems to be showing is that in the UK, at present, our marginal propensities to save or spend are the wrong way around (according to standard Keynesian theory that is).

FORBES: Why We Must Reduce the Taxes on the Rich: The Keynesian Argument

Pursuing such a vision would require very high marginal tax rates on anyone with above average production, income and wealth, which experience as well as theory shows us leads to less production.

FORBES: Fallacies Of Economic Equality That Promote Poverty